4 Answers
4

We're run into a few problems with RAM and/or Video memory addressing across a few iterations of Dell hardare where I work and found the solution to be adding pci=nommconf as a kernel option in grub - worth a try.

Are you using two CPUs? If this workstation got 18 slots and you're only getting use of 9 out of 12 memory sticks working. It almost sounds like you're only using 1 CPU. Other than that, there might be failure in your motherboard / firmware.

Advanced ECC Mode — RAS feature that extends multi-bit single device error correction to x8
DRAMs, which runs pairs of memory channels in lockstep mode. There can be a substantial hit to
memory performance when using this mode.

Spare Mode — RAS feature that allocates one rank per channel as a spare to reduce the likelihood
of correctable errors from becoming uncorrectable errors, but at a cost to memory capacity.

Mirror Mode — RAS feature with paired memory channels that provide data and transmission
fault-tolerance, but available memory capacity is reduced by 50 percent and system memory
bandwidth will decline.